I've put in a dozen or more kitchens. Flat pack type cabinets and pre-made cabinets. Easy enough. Purchase one of those very long spirit levels and spend A LOT of time getting it all within a mm of perfectly level and aligned with the wall/counter top. Please note the wall may not be perfectly straight and 90 degrees at the corner.
Then spend some money on a nice counter top and it will look like a million bucks
